Pre-filled syringes that are filled with a selected dosage of a medication are well known injection devices for administering the medication to a patient. Safety devices for covering a needle of a pre-filled syringe before and after use are also well known. Typically, these devices comprise a needle shield that is either manually moved or moved by the action of a relaxing spring to surround the needle.
A different type of safety devices known in the state of the art solves the object of providing needle safety by arranging the pre-filled syringe movable relative to a body, wherein the pre-filled syringe is retracted into the body after the injection.
The European Patent Application EP 1 321 158 A1 describes a safety device for a sheathed injection syringe. A needle guard of the safety device has a dilatable opening. A ring is movably arranged around the needle guard and is positionable over the distal portion of the needle guard so as to reconfigure the needle guard and contract the opening.
Document U.S. Pat. No. 4,871,355 discloses a needle and blood collection tube holder with a protective covering to reduce the possibility of accidental needle stick injuries. The tube holder comprises an inner and an outer tube defining a needle protection chamber. A diaphragm is mounted to the forward end of the outer tube. The diaphragm includes individual sections or leafs forming a central orifice of variable diameter adapted expand so that protective sheaths of different sizes may be inserted therein.